1. Field of the Invention
The present invention relates to a vibration mechanism applicable to a vibration isolator or an exciter and having a magnetic spring that includes a plurality of permanent magnets with the same (repulsive) magnetic poles opposed to each other.
2. Description of Related Art
Currently, various vibration models have been proposed and put to practical use. In general, vibration characteristics depend on the loaded mass and the input. It is considered that there is a correlation between the loaded mass and the curvature of load-deflection characteristics, and between the input and the hysteresis of load-deflection characteristics.
By way of example, metal springs, air springs or the like have been hitherto employed in a vibration isolator unit for suppressing vibrations transmitted to an automobile seat through a vehicle floor. When soft springs are used in the vibration isolator unit, the resonant point is shifted to a low-frequency side but the vibration transmissibility becomes high. To reduce the vibration transmissibility at the resonant point, it is necessary to enlarge the damping ratio of a damper. However, enlargement of the damping ratio results in an increase in the vibration transmissibility at high frequencies and, hence, conventional passive vibration models have a limit on their performance. Optimization under all the conditions requires an active control.
Recently, an active suspension seat has been proposed wherein an actuator mounted on an automobile seat works to active-control vibrations to enhance the ride comfort.
On the other hand, the exciter is generally used to investigate vibration characteristics of various articles or used for a vibration generating source for a machine in an amusement park.
Of the vibration mechanisms referred to above, the vibration isolator unit employing the metal springs, air springs or the like cannot enhance the ride comfort or the feeling of use by decreasing a vibration frequency of 2-12 Hz from among vibrations transmitted through the vehicle floor.
Furthermore, the active suspension seat is heavy and expensive and is also required to always activate the actuator. If the actuator is turned off, vibrations are transmitted to a seat occupant through the actuator, thus losing the ride comfort.
In addition, realization of a seat suspension unit having a low S.E.A.T. value (explained later) with a small stroke has been difficult, because the absorbency of vibration energy depends on the stroke.
On the other hand, the exciter requires an actuator for exciting or bouncing articles against the gravity thereof and is relatively complicated in construction and expensive.